Mold with tungsten carbide insert



Jan. 17, 1950 J. s. HoRvATH 2,495,064

MOLD WITH TUNGSTEN CARBIDE INSERT Filed Aug. 19, 1947 le l? ATTO/aven? Patented Jan. 17, 1950 UNITEDSTATES PATENT OFFICE MOLD WITH TUNGSTEN CARBIDE INSERT Joseph S. Horvath, Bridgeport, Conn., assignor to The Plastic Mold Die & Tool, Inc., Bridgeport, Conn., a corporation of Connecticut Application August 19, 1947, Serial No. '769,338

4 Claims.

This invention relates to molds having cavities into which moldable material is introduced to produce formed or shaped parts, and relates more particularly to molds having gates which are especially wear-resistant.

The invention is' shown as applied to a mold for forming parts of plastic material; however it should be understood that this showing is not to be taken in a restrictive sense, since the invention has utility in connection with other molds, for other uses.

Molds for the transfer molding of plastics have one or more cavitiesfor receiving and shaping the molding material, each cavity being 'connected with a channel or gate through which the molding material is forced in entering the cavity. Directly adjacent the lcavity the gate is formed with a constricted portion, which provides a thin section in the sprue that extends from the molded part, and enables the said part to be more completely formed and readily severed from the sprue without disfiguration. v

Parts of a mold are normally hardened, this being usually done byrpacking due to hardness being required mostly at the surface and because of the large mass involved and necessity to avoid warpage. In spite of this hardening, however accomplished, considerable wear is eX- perienced at the constricted portion of the gate and adjacent part` of the cavity, especially when molding with urea resins. Attempts have been made in the past to reduce this wear by the use of small Wear-resistant inserts of tungsten carbide or the like, at the constricted portions of the gates and adjacent vcavity portions. Economy 35 inthe use of this material and the brittleness of the material necessitate that such inserts be of small size, not greatly larger than the surfaces subject to Wear. Accordingly, it has been the practice in the use of wear-resistant carbides to o recess the Wearing parts and braze or silver solder such inserts in place to the Walls of the wearing parts. When attempts were made to overcome the wear at the gates of a mold by silver soldering or brazing a wear-resistant insert in the recesses in molds which had to be hardened previously, by packing, it was found that the temper or hardness of the mold was considerably impaired. In hardening, these molds are usually drawn from temperatures of approximately 1400" F. down to 350 F. Silver Soldering requires a temperature in the neighborhood of 1300 F., and brazing requires temperatures around 1700" F. Molds thus provided with inserts were less Satisfactory than if not so provided, since after a period of use the cavities themselves showed wear due to loss of hardening, thereby altering the shape of the molded product and making it necessary to discard the mold entirely.

The above diiiiculty is overcome by the present invention, which provides an improved wear-resistant mold having pack-hardened parts and having soldered wear-resisting inserts at the portions most subject to wear and in which the normal hardness of the mold parts is unimpaired so that the cavities thereof do not wear unduly, the inserts being securely held in place by solder at the constricted portions of the gates and adjacent portions of the mold cavities. This is accomplished by recessing or cutting away the mold parts to a much greater extent than is normally required to accommodate the inserts, and by providing special steel mounting blocks to which the inserts may be soldered, and which are sized to t the enlarged recesses, and secured to the mold parts by means not involving heat, as withgreatest abrasive action, may be provided with carbide or equivalent wear-resisting inserts securely soldered in place, IWhile the remainder of the mold vretains its normal hardness, thereby considerably increasing the mold life. Moreover,

since the mounting blocks are secured in place by bolts, the carbide inserts and blocks may be removed from a mold and readily replaced if necessary, thus saving the mold from being scrapped should one set of inserts become worn:

too much prior to deterioration beyond use of the rest of the mold.

Other features and advantages will hereinafter appear.

Inv the accompanying drawings:

Figure l is a fragmentary sectional ViewA through an improved mold made in accordance with the invention. l

Fig. 2'is a view taken on line 2-2 of Fig. 1, and Fig. 3 is a view taken on line 3-3 of Fig. 1. Y

As shown, an improved mold made in accordance with the invention may comprise a cavity block I which is cooperable with a force block II, the said blocks being so disposed and shaped as to provide a molding cavity I2 between them. The blocks I0 and H may be advantageously formed of steel, pack hardened and drawn for example to a temperature in the neighborhood of 350 F.

Associated with the blocks I0 and I I is a runner block I3 having a channel or gate I4 and a pot I5 in which the molding material 4is carried-the said runner block and pot being also of packhardened steel. As shown in Figs. land ZtheV gate I4 connects with the cavity I2-andis constricted at the point of connection', and Whenthe mold is put in use most wearyvill` loccur atthe` constricted part of the gate I4 and the adjacent part of the cavity I2. appreciable despite the pack-hardening of the mold parts-,L especially when moldingf-with urearesins.

According to this invention, smallA tungsten carbide or equivalent Wear-resistant-inserts are provided in the mold at the locations most likely to wear so as to prolong-"moldlife,l andvarexsecured against dislodgement byy soldering,l as with' silver vsolder or brazing soldenwithout impairing the hardness of the cavity blockiIil,l force'blockA II, runner block- I3 or 'pot I5. li/ioreover, theinserts are mounted so astobereadilyremovable and replaceable, thereby further `increasingthe useful life range of themold;

In accomplishing this, referring to Fig. 1,'thecavity block I Il and force blockj I I of themoldad-4 jacent the constrictedy portion of the gate. Mare deeply recessedor cut away,- to asmuch greater extent than necessary to accommodate-:the carbideinserts, and'steel mounting blocks .I6 and 'I'I are secured to the'blocks I0 and II respectively by'cap screws I8. It Willbezseen that the-mounting blocks I6 andA I'I replace the=stock of the'mold blocks I0 and II at the constrictedportion of thegate I4. Solderedto the mountingblocks I6F andr I1 :are small. carbide .inserts I9. and= .".ll reispectvely, the insert I9 beingedgewise tothe` insert 20, and the-latter insert having adshallovv` recess 2| inY its broadiace presentedtotheinsert I9.

The mounting blocks.Y I6 and I I and carbide inserts I9 and 2li respectivelysoldered thereto are shaped to form parts of the cavityl2 and gate I4,

and the said inserts constitutethe constricted..

portion of the gate and adjacent portionsof the cavity which would normally show the most Wear. The blocks I6 and I1 are formed of air-'hardening or of high speed steel or the'equivalent having a high decalescence temperatureV such` that the blocks may be hardened` and then have the inserts I9 vand 20 respectively soldered to them, as by silver soldering or brazing for example, Without adverselylaiecting their temper. Thus thesurfaces of the mounting blocks I6 and II which are Such wear may bequiten equivalent Wear-resistant inserts anchored by solder and mounted at the points normally most likely to show wear in the mold, all without impairing the temper or hardness of the mold parts, and therefore greatly increasing the useful life of the mold. The carbide inserts and mounting blocks therefor are also readily removable from the mold and replaceable, and inzmulti-cavity molds may be made interchangeable if desired, resulting in an extremely flexible arrangement which reduces downtime and maintenance, and provides for long life of the mold blocks.

Variations and modifications may be made within4 the scope Aof this invention and portions of lthe improvements may be used without others.

I claim:

LA wear-resistant mold comprising a body formed of hardened steel the hardness of which is-impaired by temperatures required to solder it, said body having a cavity and having a gate connected with. the cavity; and an insert in said body, saidninsert comprising. a block' of hardened steel, the hardness of which'is not substantially irnpaired by temperatures required to'solder it, and said insert further comprising armember of wearresistant alloy-solderedto'said block, said member constitutingpart of the Wallof the gate at aconstricted portion ofthe gateand lbeing subjected to .therlow of `molding material from the gate to the cavity, and said block being secured to said body.

2; A'wearfresistant mold comprising a two-part body formed of hardened steel the hardness of which' isimpaired by temperatures required to solder it, said body having va cavity and having a gate-'connected with thefcavity; and a pair of inserts in said body, each of said insertscomprising a block of hardened steel, the hardness of which isnot impaired rbytemperatures required to solder it, and furthercomprising 'a member of Wear-resistant alloy' soldered `to said block, the wear-resistant members of said inserts constituting the -entire wall 'of the -gate at a constricted portion'of the gate andbeing subjected to the flow of'molding; material from' the gatetothe cavity, and'said blocks being clamped to said body.

3. A wear-resistant mold comprising a body formed of hardened steel, the hardness of which is impaired by temperatures required to solder it, said body having a cavity and having a gate connectedwith the cavity; and an insert in said body, said insert comprising a block of hardenedsteel, the hardness of which is not impaired by ternperaturesrequired to solder it, andsaid insert further comprising a wear-resistant member of tungsten carbideA soldered .to said block, said member constituting part of the wall 'of said gate at a constricted portion of the gate and being subjected to the flow of molding material. from the gate to the cavity, vand said block being removably secured to said body.

4. A wear-resistant mold comprising a body formed of hardenedV steel, .the hardness of which is impaired by temperatures required to solder it, saidbody having a molding cavity and having a gate formed with a Vconstricted portion connected with the cavity; Wear-resistantmeans shaped to provide apassage for molding material and adaptedto constitute lan insert in said body; and a hardened steel mounting for said Wear-resistant means, said mountingv being: secured to said body byheat-free means, andV the hardness of said mounting being not impaired by temperatures requiredto solder it, said wear-.resistant means be-- REFERENCES CITED The following references are of record in the fue of this patent:

UNITED STATES PATENTS Number Name Date 1,879,485 Ramage Sept. 27, 1932 2,644,986 Horton June 23, 1936 2,185,625 Bird Jan. 2, 1940 OTHER REFERENCES Machinery August 1946, pages 150-156.

10 (Copy in Div. 58.) 

3. A WEAR-RESISTANT MOLD COMPRISING A BODY FORMED OF HARDENED STEEL, THE HARDNESS OF WHICH IS IMPAIRED BY TEMPERATURES REQUIRED TO SOLDER IT, SAID BODY HAVING A CAVITY AND HAVING A GATE CONNECTED WITH THE CAVITY; AND AN INSERT IN SAID BODY, SAID INSERT COMPRISING A BLOCK OF HARDENED STEEL, THE HARDNESS OF WHICH IS NOT IMPAIRED BY TEMPERATURES REQUIRED TO SOLDER IT, AND SAID INSERT FURTHER COMPRISING A WEAR-RESISTANT MEMBER OF TUNGSTEN CARBIDE SOLDERED TO SAID BLOCK, SAID MEMBER CONSTITUTING PART OF THE WALL OF SAID GATE AT A CONSTRICTED PORTION OF THE GATE AND BEING SUBJECTED TO THE FLOW OF MOLDING MATERIAL FROM THE GATE TO THE CAVITY, AND SAID BLOCK BEING REMOVABLY SECURED TO SAID BODY. 